I have a RunTime solution containing scripts that open various pdf's in new windows. A user complained that the window opened, but was empty. He was using Windows 10 and had 'MS Edge' as a reader. However, when he downloaded Acrobat Reader, problem solved.
Having read: Viewing PDF in Container Field
It appears the problem is in Windows, not Mac (it has Preview to fall back on), and that though other pdf readers will work, they sometimes don't but installing Acrobat Reader solves the problem.
Would the above sum up the advice I should give to users?